WASHINGTON (CN) – The National Oceanic and Atmospheric Administration’s guidance document for acoustic thresholds for marine mammals, expected a year ago, was delayed again to incorporate the Navy’s input. The document is important for “consistent implementation” of laws protecting approximately 125 marine mammal species from the effects of human-caused ocean noise, such as seismic air guns used in oil and gas exploration, construction activities, or underwater detonations and sonar used in military readiness activities.
“This will be the first time acoustic threshold levels have been presented in a single, comprehensive document,” the agency said. The project was initiated in 2013 and was expected to be completed in the winter of 2014-2015. But, as the agency was addressing public comments from a second comment period, new methodology developed by the Navy, one of the biggest sources of harmful ocean noise pollution, spurred revisions to the draft document, requiring another public comment period. The new projected date for the final document is May of this year.
Marine mammals, such as whales, dolphins, seals and sea lions, use sound to navigate, find food and communicate. A recent study by NOAA and its partners seven miles deep in the Mariana Trench found that the ocean is not a quiet place. The noise is nearly constant, with natural sounds of earthquakes, typhoons, and the songs of marine mammals, and human-caused sources, such as the sounds of ship propellers, pile drivers and resource exploration. Sound from seismic air guns, for instance, is known to travel up to 2,500 miles through the water, the agency said.
When a construction project, military training exercise or other endeavor is projected to cause underwater sounds that could harm protected species of marine mammals, NOAA must evaluate the potential harm before issuing Letters of Authorization. Both the Endangered Species Act and the Marine Mammal Protection Act put limits on mortality or other harm that can be allowed, which is why the guidance document is needed.
A case brought by the Natural Resources Defense Council, Cetacean Society International, Animal Legal Defense Fund and others, before the U.S. District Court, District of Hawaii, ruled in April 2015 that the agency was remiss in authorizing “nearly 9.6 million underwater assaults on whales and dolphins” under a five-year authorization of the Navy’s training activities.
While it might be considered that NOAA has put the fox in charge of guarding the henhouse, the agency insists that the new methodology for assessing the thresholds developed by the Navy is “the best available science.” When asked for more specifics regarding this, NOAA’s spokesperson Connie Barclay said, “The Navy’s SPAWAR Systems Center Pacific is one of five laboratories in the world conducting research on the effects of noise on marine mammal hearing. Specifically, the scientist conducting these studies, Dr. James Finneran, is considered an expert in the field, and in addition to the Navy, has served as an expert on a scientific panel in 2007 making recommendations for noise exposure thresholds.” Barclay also noted that NOAA had the Navy’s methodology independently peer reviewed.
In contrast to the metrics previously used to establish thresholds, the complex and highly technical specifications in the guidance document set limits for expected temporary or permanent hearing threshold shifts (hearing loss) using updated criteria. Sound sources are divided into two groups, impulsive (such as air guns and impact pile drivers) and non-impulsive (such as sonar and vibratory pile drivers). Sound is also measured in terms of peak sound pressure levels and cumulative duration of exposure.
Because not all marine mammals “hear and use sound in the same manner,” the agency has now divided the animals into groups, such as eared and earless seals, and low-, mid- and high-frequency whales and dolphins.
The Navy provided NOAA with its January 2015 technical paper, Acoustic Effects Analysis, describing its proposed methodology for updating auditory weighting functions and subsequent numeric thresholds for predicting temporary and permanent auditory effects on marine animals exposed during Navy training and testing activities, NOAA’s Barclay said.
According to the announcement of the revisions, the Navy’s recommendations include updates to the method for predicting and establishing auditory thresholds for low-frequency marine mammals, moving the white-beaked dolphins from a mid-frequency to a high-frequency classification, incorporating new information on harbor porpoise auditory thresholds, excluding some data regarding seals and sea lions, removing peak sound pressure level acoustic threshold levels for non-impulsive sounds and updating the method for deriving peak acoustic threshold levels for functional hearing groups where no data are available.
The agency notes that “in some situations (e.g., depending on sound source, species, and duration of exposure), updated acoustic thresholds may result in more exposures than previously applied thresholds, while in others they may result in less exposures.”
In addition, the guidance document focuses solely on affects of human-caused sounds on the hearing of protected marine mammals. Behavioral responses are still being studied, the agency said.
Comments on the guidance document revisions are due March 30.
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